1. Field of the Invention
This invention relates to projectiles and in particular to projectiles carrying fin-stabilised flechettes.
2. Description of the Prior Art
A fin-stabilised flechette is a dart-like projectile used to penetrate a target. A flechette, as disclosed in e.g. U.S. Pat No. 3,954,060 (Haag et al), may be formed as a small metal element having a pointed end and a finned rearward end for stabilising the flechette with the pointed end disposed forwardly in flight.
Projectiles which dispense a plurality of flechettes are well-known. Typically, the flechettes are arranged around and mounted on a central core of the projectile. When proximity to a target is detected, the flechettes are dispersed by explosive means and travel outwardly as well as in the forward direction, diverging away from the trajectory on which the projectile is moving. This type of projectile is suitable where there are multiple targets or where the flechettes can be dispersed close to the target.
Alternatively, as disclosed in e.g. U.S. 3,954,060, the flechettes may be disposed in tiers separated by annular spacers within a casing portion. The projectile spins in flight. At a preselected time in the flight of the projectile, the casing portion is dispersed by explosive means. The centrifugal force developed by the spin of the projectile causes the annular spacers to break up, thereby releasing the flechettes which themselves move laterally outwardly under the centrifugal action of the spinning projectile to be dispersed in a generally conical pattern as individual fragments. The dispersion pattern of the flechettes may be adjusted for optimum effectiveness by suitable correlation of the forward velocity of the projectile to its velocity of spin.
Such known projectiles are however not suitable for intercepting a target having a very high velocity, such as a missile warhead re-entering the atmosphere, when the relative velocity of the target and projectile could be Mach 15-20. With such high relative velocities, proximity fuses do not operate sufficiently rapidly or accurately for the flechettes to intercept the target. If, however, the flechettes were dispersed earlier, at some pre-selected time, they would diverge too much from the projectile trajectory to be effective. Even when the flechettes do align themselves parallel to the projectile trajectory due to their fin-stabilisation, it is difficult to pre-determine the distance from the projectile trajectory at which this will happen.